The microstructures and hardness property of dual two-phase intermetallic alloys that are composed of various kind of volume fractions of geometrically closed packed (GCP) Ni 3 Al(L1 2 ) and Ni 3 V(D0 22 ) phases was studied. Higher volume fraction of primary Ni 3 Al precipitates was observed in the Ti and Nb added alloys when keeping Al content the same. Also, the microstructures in the eutectoid (channel) region consisting of Ni 3 Al+Ni 3 V were sensitive to alloying addition. The hardness of dual two-phase intermetallic alloys was basically explained by mixture rule in hardness between primary Ni 3 Al precipitates and eutectoid region. Nb and Ti addition raised hardness of dual two-phase intermetallic alloys by solid solution hardening in the constituent phases. This hardening was more significant in Nb addition than in Ti addition. In addition to hardness owing to the mixture rule, additional hardening arising from interfacial area between primary Ni 3 Al precipitates and eutectoid region was found. With increasing Ni 3 Al/channel (eutectoid) interfacial area, the additional hardening increased. As temperature increases, the additional hardening monotonously decreased for the base and Nb added alloys but little decreased for the Ti added alloys.

A superconducting joint of unreacted monofilament internal magnesium diffusion-processed magnesium diboride (MgB 2 ) wires was fabricated by exploiting the phenomenon of magnesium diffusion into the boron layer inside the superconducting joint. Unprecedentedly, the joint was able to carry an almost identical transport current compared to the bare wire in a 2−7 T magnetic field at 20 K. The joint also exhibited very low joint resistance of 2.01 × 10 −13 Ω in self-field at 20 K. Among commercially available superconductors, this work is the first to successfully realize a superconducting joint that is capable of transferring current from one conductor to another without any notable degradation under strong magnetic fields. This work demonstrates great potential to apply MgB 2 in a range of practical applications, where superconducting joints are essential.

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Biomedical applications rely on semiconductor quantum dots (QDs) exhibiting electroluminescence (EL) properties in the wavelength range between 1.0 and 1.7 μm (called the second near-infrared window, NIR-II). However, developing heavy-metal-free QDs remains a challenge. Herein, we report, for the first time, a colloidal silicon QD light-emitting diode (Si-QLED), which exhibits an EL spectrum with a peak at 1.0 μm along with a high external quantum efficiency (EQE) value of 4.84%, which is close to the record value among reported NIR-II EL devices. SiQDs as optically active layers are synthesized by thermal disproportionation of hydrogen silsesquioxane derived from triethoxysilane, followed by hydrofluoric etching. The photoluminescence quantum yield of SiQDs is improved up to 53% by thermal hydrosilylation of 1-decene, followed by careful extraction of highly emitting QDs using size exclusion chromatography. Si-QLEDs have an inverted device architecture with multilayers, leading to stable emission properties even at a high applied voltage. Furthermore, we demonstrate a spectral shape tuning of the EL spectra by taking advantage of a large Stokes shift between the optical absorption and emission, the property inherent to QDs of indirect band gap Si crystals.

The deformation-induced martensitic transformation is a phenomenon that significantly improves the mechanical properties of steels, and is well known to be beneficial for the rolling contact fatigue (RCF) of bearings. In the present study, the characteristics of the deformation-induced martensitic transformation in the RCF of carburized, quenched and tempered SAE4320 steel were investigated in detail using scanning electron microscopy with electron backscattering diffraction and transmission electron microscopy with automated crystal orientation mapping. These analyses clarified that different variants of the extremely fine deformation-induced martensites as small as several tens of nm were formed within an austenite grain with RCF, and the martensites were speculated to have the Kurdumov-Sachs or the Nishiyama-Wasserman relationship with the retained austenite. Furthermore, the deformation-induced martensites were preferentially formed within the retained austenite grains rather than at the interface between the tempered martensite and retained austenite. This suggests that the deformation-induced martensites were formed from some localized regions that were plastically introduced within the retained austenite grains.